An automobile conventionally employs a hollow, tubular drive shaft to transmit torque from the transmission to the differential gears. Such drive shafts often produce annoying NVH (i.e., noise, vibration, and harshness). Accordingly, it is desirable to dampen NVH to provide for a quieter and smoother ride. Furthermore, it is desirable to prevent vibration to avoid mechanical failure from the loosening of assembled vehicle parts.
Several commonly assigned patents address NVH reduction. For example, U.S. Pat. No. 4,909,361 to Stark et al. discloses a drive shaft damper having a base tube or core formed of helically wound paper. A helical retaining strip, such as ethylene propylene diene monomer rubber (i.e., EPDM) is fixed to the core to engage the bore of the drive shaft.
Another example is U.S. Pat. No. 5,976,021 to Stark et al. U.S. Pat. No. 5,976,021 improves the drive shaft damper disclosed in U.S. Pat. No. 4,909,361 by including sealed ends and an innermost layer of waterproof material, such as aluminum foil.
Yet another example is U.S. Pat. No. 5,924,531 to Stark et al. U.S. Pat. No. 5,924,531 discloses a vibration damping shaft liner having a cylindrical core and a corrugated layer wound around the core in alternating helical grooves and flutes.
Each of the above-referenced patents is herein incorporated by reference in its entirety.
The drive shaft dampers disclosed in the foregoing, commonly assigned patents are well suited for their intended purposes. That notwithstanding, ever more manufacturers are producing drive shafts having standardized end diameters. Such drive shafts accommodate universal joint flanges, which attach the drive shaft to the gearboxes and differentials in motor vehicles. This standardization is achieved by reducing the diameter at the respective drive shaft ends, a process referred to as “swaging.”
The reduction of the drive shaft ends necessitates the insertion of the damper into the drive shaft prior to the swaging process. Thereafter, the drive shaft is heat treated under extreme conditions (e.g., 350° F.) for a period sufficient to strengthen the drive shaft (e.g., about 6-8 hours).
Accordingly, there is a need for drive shaft dampers that can provide improved NVH reduction and withstand the extreme heat conditions required for modern drive shaft manufacturing. In particular, there is a need for resilient and durable drive shaft dampers that can be inserted into drive shafts prior to swaging and that can be manufactured efficiently and cost-effectively.